PATENT LITERATURE 1 and 2 disclose using, as an ion conductor of a fuel cell, a perovskite type oxide such as barium zirconate doped with yttrium (hereinafter, referred to as “BZY”), barium cerate doped with yttrium, and a mixed oxide of barium zirconate/barium cerate doped with yttrium.
NON PATENT LITERATURE 1 states that BaY2NiO5 is generated as a by-product in the case where an anode of a fuel cell is formed by sintering the BZY and nickel oxide. Furthermore, NON PATENT LITERATURE 1 states that the BaY2NiO5 decomposes in an atmosphere containing water, carbon dioxide, or hydrogen, to generate decomposition products such as barium hydroxide [Ba(OH)2] and barium carbonate [BaCO3].